U.S. patent application number 15/066382 was filed with the patent office on 2016-06-30 for cooler and semiconductor device having cooler.
The applicant listed for this patent is FUJI ELECTRIC CO., LTD.. Invention is credited to Takahiro KOYAMA, Noriho TERASAWA.
Application Number | 20160190038 15/066382 |
Document ID | / |
Family ID | 54071461 |
Filed Date | 2016-06-30 |
United States Patent
Application |
20160190038 |
Kind Code |
A1 |
KOYAMA; Takahiro ; et
al. |
June 30, 2016 |
COOLER AND SEMICONDUCTOR DEVICE HAVING COOLER
Abstract
A cooler for cooling a semiconductor module includes a top
plate; a jacket having a side plate and a bottom plate and firmly
fixed to the top plate; a refrigerant inflow port through which a
refrigerant flows into a space surrounded by the top plate and
jacket; a refrigerant outflow port through which the refrigerant
flows out from the space; a plurality of fins firmly fixed to the
top plate and disposed separately on each of the left and right
relative to a main refrigerant path in the jacket to be inclined
toward the inflow side of the main refrigerant path; heat transfer
pins disposed on the top plate on the refrigerant inflow sides of
the fins; and a curved plate-like bimetal valve having one end
connected to each respective heat transfer pin and another free
end.
Inventors: |
KOYAMA; Takahiro;
(Matsumoto-shi, JP) ; TERASAWA; Noriho;
(Matsumoto-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FUJI ELECTRIC CO., LTD. |
Kawasaki-shi |
|
JP |
|
|
Family ID: |
54071461 |
Appl. No.: |
15/066382 |
Filed: |
March 10, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2015/052946 |
Feb 3, 2015 |
|
|
|
15066382 |
|
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|
Current U.S.
Class: |
257/693 ;
165/80.4 |
Current CPC
Class: |
H01L 23/3675 20130101;
F28F 3/048 20130101; H01L 23/3677 20130101; H01L 23/3735 20130101;
H05K 7/20927 20130101; F28F 3/12 20130101; F28F 27/02 20130101;
H01L 23/49838 20130101; F28F 3/022 20130101; H01L 23/3121 20130101;
H01L 25/0655 20130101; F28D 15/00 20130101; F28F 13/12 20130101;
F28F 3/02 20130101; F28F 2255/04 20130101; H01L 23/473 20130101;
H01L 2924/00 20130101; H01L 2924/0002 20130101; H01L 2924/0002
20130101; H01L 23/3736 20130101; H01L 23/3672 20130101 |
International
Class: |
H01L 23/473 20060101
H01L023/473; H01L 23/373 20060101 H01L023/373; H01L 23/498 20060101
H01L023/498; F28F 3/02 20060101 F28F003/02; H01L 23/31 20060101
H01L023/31; F28D 15/00 20060101 F28D015/00; F28F 13/12 20060101
F28F013/12; H01L 23/367 20060101 H01L023/367; H01L 25/065 20060101
H01L025/065 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 14, 2014 |
JP |
2014-051037 |
Claims
1. A cooler for cooling a semiconductor module, comprising: a top
plate; a jacket having a bottom plate, a side plate firmly fixed to
the top plate, and a main refrigerant path therein; a refrigerant
inflow port through which a refrigerant flows into a space
surrounded by the top plate and jacket; a refrigerant outflow port
through which the refrigerant flows out from the space; a plurality
of fins firmly fixed to the top plate and disposed separately on
left and right relative to the main refrigerant path in the jacket
to be inclined toward an inflow side of the main refrigerant path;
heat transfer pins disposed on the top plate on the refrigerant
inflow side of the fins; and a curved plate-like bimetal valve
having one end connected to each heat transfer pin, and another
free end.
2. The cooler according to claim 1, wherein an inclination angle of
the fin is in a range of 30 degrees or more and 60 degrees or less
with respect to the main refrigerant path as a reference.
3. The cooler according to claim 1, wherein the refrigerant is a
liquid.
4. The cooler according to claim 3, further comprising a blocking
plate on a downstream side of the main refrigerant path before the
refrigerant outflow port.
5. The cooler according to claim 3, wherein an installation
distance between adjacent heat transfer pins is twice or more as
large as a distance between adjacent fins.
6. The cooler according to claim 3, wherein the bimetal valve has a
structure such that the bimetal valve changes to a first shape,
which is curved in a refrigerant inflow direction, and to a second
shape which becomes closer to linear as a temperature becomes
higher than that in the first shape, and in the first shape, a
distance between the free end of the bimetal valve and the fin
adjacent thereto is equal to a distance between adjacent fins.
7. The cooler according to claim 6, wherein the bimetal valve
includes a first metal piece, and a second metal piece joined
together, the second metal piece having expansion coefficient
higher than that of the first metal piece, the first metal piece is
an iron-nickel alloy plate, and the second metal piece is formed of
one or a plurality of metals selected from the group consisting of
manganese, chromium, and copper, added to an iron-nickel alloy
plate.
8. The cooler according to claim 7, wherein a thickness of the
bimetal valve is 0.5 mm or more and 5 mm or less.
9. A semiconductor device comprising: the cooler according to claim
3; a circuit substrate having an insulating substrate, a circuit
portion on an upper surface of the insulating substrate, and a
metal portion on a lower surface of the insulating substrate; a
semiconductor chip electrically connected to the circuit portion,
which is cooled by the cooler; a first external terminal connected
to the semiconductor chip; a second external terminal connected to
the circuit portion; and a resin portion which houses the circuit
substrate, the semiconductor chip, the first external terminal, and
the second external terminal, except a surface on an opposite side
of the metal portion from the insulating substrate, one end of the
first external terminal, and one end of the second external
terminal, wherein the plurality of fins is thermally connected to
the metal portion, and the heat transfer pins are disposed below
the insulating substrate.
10. The semiconductor device according to claim 9, further
comprising: a plurality of intermediate assemblies, each having the
circuit substrate, the semiconductor chip, the first external
terminal, and the second external terminal; a metal base disposed
between a plurality of metal portions and the top plate; a first
connection member which thermally connects the plurality of metal
portions and the metal base; and a second connection member which
thermally connects the metal base and top plate.
11. The semiconductor device according to claim 9, wherein the top
plate is the metal portion.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This is a continuation application of PCT/JP2015/052946
filed on Feb. 3, 2015, which claims priority of Japanese Patent
Application No 2014-051037 filed on Mar. 14, 2014, the disclosure
of which is incorporated herein as a reference.
TECHNICAL FIELD
[0002] The present invention relates to a cooler, which cools a
semiconductor module, and a semiconductor device having the
cooler.
BACKGROUND ART
[0003] Heretofore, a semiconductor module and a cooler thereof are
formed in the following way.
[0004] FIGS. 5(a)-5(c) are diagrams with a heretofore known
semiconductor module 500a mounted on a cooler 500b, wherein FIG.
5(a) shows a main portion plan view, viewed through a bottom plate
of the cooler from the rear, FIG. 5(b) shows a main portion
sectional view taken along line 5(b)-5(b) in FIG. 5(a), and FIG.
5(c) shows a main portion sectional view taken along the line
5(c)-5(c) in FIG. 5(a).
[0005] The semiconductor module 500a includes a metal base 51, six
circuit substrates 54 each having an insulating substrate 54a, a
circuit portion 54b on the front surface of the insulating
substrate 54a, and a metal portion 54c on the rear surface of the
insulating substrate 54a, and a plurality of semiconductor chips
58, each being firmly fixed to each circuit portion 54b. The
semiconductor module 500a includes first external terminals 59a
each being connected to each semiconductor chip 58, second external
terminals 59b each being connected to each circuit portion 54b, and
a resin portion 60 sealing the whole with the rear surface of the
metal base 51, leading end portions of the first external terminals
59a, and leading end portions of the second external terminals 59c
being exposed. One wherein the circuit substrate 54, to which the
semiconductor chip 58 is firmly fixed, the first external terminal
59a, and the second external terminal 59b are assembled by a
joining material, such as a solder, is called an intermediate
assembly 52. Herein, a case in which six intermediate assemblies 52
are mounted is shown. Normally, each of the intermediate assemblies
52 includes, for example, an IGBT (insulated gate bipolar
transistor) chip and an FWD (free wheeling diode) chip connected in
inverse parallel thereto.
[0006] The cooler 500b includes a top plate 70, a jacket 71 fixed
to the top plate 70, and fins 72, disposed in the jacket 71, which
are disposed parallel to the stream of cooling water and firmly
fixed to the top plate 70. The jacket 71 is an open-topped casing
having a side plate 71a and bottom plate 71b, and a refrigerant
inflow port 73 and a refrigerant outflow port 74 are provided in
the side plate 71a. The fins 72 are disposed uniformly in parallel
in the jacket 71, and the fins 72 have a flat shape. Each
intermediate assembly 52 is cooled by flowing a refrigerant between
adjacent fins 72.
[0007] A semiconductor device 500 is formed of the semiconductor
module 500a and the cooler 500b, wherein for example, a thermal
compound 78 is applied to the metal base 51 of the semiconductor
module 500a, and the semiconductor module 500a is fixed to the
cooler 500b by bolts, bands, or the like.
[0008] Herein, the cooling of the semiconductor module 500a on
which is mounted the plurality of semiconductor chips 58 is carried
out by one cooler 500b, and the control of the cooling capacity of
the cooler 500b is carried out by adjusting the flow rate of the
refrigerant.
[0009] For example, PTL 1 describes a heat sink wherein cooling
fins having a bimetal structure, with two metals of each fin
warping in opposite directions to each other depending on
temperature, increase surface area, thus improving the cooling
capacity.
[0010] Also, PTL 2 describes a cooing device wherein heat is
transferred to a bimetal from an uncooled body by a heat pipe, and
a flap is formed by a change in shape of the bimetal, thus changing
the volume of cooling air.
[0011] Also, PTL 3 describes a semiconductor device cooling device
which transfers heat generated from each semiconductor chip of a
multichip module with a substrate to which a plurality of
semiconductor chips is firmly fixed, to a cooling jacket provided
opposite the module, and thus collectively cooling the
semiconductor chips for each module, wherein the temperatures of
the semiconductor chips on the substrate are individually detected,
and the coolings of the semiconductor chips are individually
controlled based on the detected temperatures.
CITATION LIST
Patent Literature
[0012] PTL 1: JP-A-4-303954
[0013] PTL 2: JP-A-2011-144900
[0014] PTL 3: JP-A-4-152659
SUMMARY OF INVENTION
Technical Problem
[0015] With the semiconductor device 500 shown in FIGS. 5(a)-5(c),
a temperature distribution is sometimes formed in the principal
surface due to the difference in the individual characteristics and
operating condition between the plurality of mounted semiconductor
chips 58. For example, FIG. 6 shows a place 81 which reaches a high
temperature when the semiconductor chip 58 operates. The insulating
substrate 54 immediately below the semiconductor chip 58 high in
temperature also reaches a high temperature at the place 81.
Supposing that stream 80 is flowing uniformly between the fins 72
and has no difference in cooling capacity, the temperature of the
stream 80 sometimes rises 20.degree. C. to 30.degree. C. at the
place 81 compared with at the other places.
[0016] Also, when there is a difference in temperature between the
semiconductor chips 58, the performance of the semiconductor device
500 is determined by the maximum operating temperature of the
semiconductor chip 58 which reaches a highest temperature.
[0017] Also, when there is a temperature distribution in the
semiconductor device 500, there is the possibility that a
difference in heat expansion occurs between the members of the
intermediate assembly 52, and the members change in shape, thus
impairing reliability.
[0018] The PTLs propose various measures, but not sufficiently. For
example, it is not described in PTL 1 that bimetal valves are
mounted to the cooler. It is not described in PTL 2 that the
cooling capacity is enhanced by increasing the amount of cooling
medium at the place high in temperature in the cooler. In PTL 3,
the refrigerant hits perpendicularly toward the rear surface side
of the semiconductor chips, and it is not described that a cooling
medium (water) is circulated in a horizontal direction.
[0019] An object of the invention is to solve the problems and
provide a cooler, having a small number of parts and a simple
structure, which can automatically enhance cooling capacity when at
high temperature, and a semiconductor device which is easy to
assemble.
Solution to Problem
[0020] In order to achieve the object, a cooler of the invention
cools a semiconductor module, and includes a top plate; a jacket,
having a side plate and a bottom plate, the side plate of which is
firmly fixed to the top plate; a refrigerant inflow port through
which a refrigerant flows into a space surrounded by the top plate
and the jacket; a refrigerant outflow port through which the
refrigerant flows out from the space; a plurality of fins firmly
fixed to the top plate, and disposed separately on each of the left
and right of a main refrigerant path in the jacket to be inclined
toward the inflow side of the main refrigerant path; heat transfer
pins disposed in positions on the top plate on the refrigerant
inflow sides of the fins; and a curved plate-like bimetal valve,
one end of which is connected to each heat transfer pin, and the
other end of which is a free end.
[0021] According to the cooler of the invention, the flow rate of
the refrigerant is automatically increased by the bimetal valves
when a semiconductor chip reaches a high temperature, and it is
thus possible to suppress arise in temperature of the semiconductor
chip. Also, as the cooler has a small number of parts and a simple
structure, it is easy to assemble the cooler.
[0022] Also, in the cooler of the invention, it is desirable that
the inclination angle of the fins is in a range of 30 degrees or
more and 60 degrees or less with the main refrigerant path as a
reference.
[0023] According to this kind of structure, it is possible to
effectively take in the stream of the refrigerant flowing between
the fins from the main refrigerant path.
[0024] Also, in the cooler of the invention, it is desirable that
the refrigerant is a liquid.
[0025] According to this kind of structure, as the specific heat of
the refrigerant is high compared with a gas, it is possible to
enhance cooling capacity.
[0026] Also, in the cooler of the invention, it is desirable to
include a blocking plate on the downstream side of the main
refrigerant path and before the refrigerant outflow port.
[0027] According to this kind of structure, as pressure loss
increases compared with when the refrigerant flows from the main
refrigerant path directly to the refrigerant outflow port, it is
possible to increase the flow rate of the refrigerant flowing
between the fins on the upstream side of the blocking plate. Then,
it is possible to enhance the cooling capacity of the cooler.
[0028] Also, in the cooler of the invention, it is desirable that
the installation distance between adjacent heat transfer pins is
twice or more as large as the distance between adjacent fins.
[0029] According to this kind of structure, it is possible to
prevent the mutual interference between the bimetal valves.
[0030] Also, in the cooler of the invention, it is desirable that
the bimetal valve can change to a first shape, which is curved in a
refrigerant inflow direction, and to a second shape which becomes
closer to linear as the temperature becomes higher than that in the
first shape, and that in the first shape, the distance between the
free end of the bimetal valve and the fin adjacent thereto is equal
to the distance between adjacent fins.
[0031] According to this kind of structure, it is possible to take
in more of the refrigerant in the second shape than in the first
shape. Then, the bimetal valve in a portion exposed to a high
temperature changes to the second shape, thus enabling an increase
in the amount of refrigerant taking in.
[0032] Also, in the cooler of the invention, it is desirable that
the bimetal valve has a first metal piece and a second metal piece
joined together. The second metal piece is higher in expansion
coefficient than the first metal piece. The first metal piece is an
iron-nickel alloy plate, and the second metal piece is formed such
that one or a plurality of metals selected from the group
consisting of manganese, chromium, and copper are added to an
iron-nickel alloy plate.
[0033] According to this kind of structure, it is possible to
obtain a bimetal valve including the first shape and second
shape.
[0034] In the cooler of the invention, it is desirable that the
thickness of the bimetal valve is 0.5 mm or more and 5 mm or
less.
[0035] According to this kind of structure, it is possible to
obtain a bimetal valve including a desired amount of change in
shape.
[0036] Also, a semiconductor device of the invention includes any
one of the heretofore described coolers, a circuit substrate having
an insulating substrate, a circuit portion on the upper surface of
the insulating substrate, and a metal portion on the lower surface
of the insulating substrate; a semiconductor chip, electrically
connected to the circuit portion, which is cooled by the cooler; a
first external terminal connected to the semiconductor chip; a
second external terminal connected to the circuit portion; and a
resin portion which houses the circuit substrate, the semiconductor
chip, the first external terminal, and the second external
terminal, except the surface on the opposite side of the metal
portion from the insulating substrate, one end of the first
external terminal, and one end of the second external terminal,
wherein the plurality of fins is thermally connected to the metal
portion, and the heat transfer pins are disposed below the
insulating substrate.
[0037] According to this kind of structure, the bimetal valve below
the semiconductor chip exposed to a high temperature changes in
shape due to heat, and the amount of refrigerant taken in
increases. Then, the semiconductor chip thereabove is effectively
cooled.
[0038] Also, in one aspect of the semiconductor device of the
invention, the heretofore described semiconductor device includes a
plurality of intermediate assemblies each having the circuit
substrate, the semiconductor chip, the first external terminal, and
the second external terminal; a metal base disposed between a
plurality of the metal portions and the top plate; a first
connection member which thermally connects the plurality of metal
portions and the metal base; and a second connection member which
thermally connects the metal base and top plate.
[0039] According to this kind of structure, as the metal base is
disposed between the metal portions and the top plate, it is
possible to suppress a change in shape occurring due to the
difference in heat expansion coefficient between the members with
respect to a cooling/heating cycle occurring with an actuation and
stop of the semiconductor device, and thus possible to strengthen
the rigidity of the cooler.
[0040] Also, in another aspect of the semiconductor device of the
invention, in the heretofore described semiconductor device, the
top plate is the metal portion.
[0041] According to this kind of structure, as the heat transfer
path from the semiconductor chips to the fins is short, it is
possible to increase the heat transfer rate. Further, it is
possible to enhance the cooling capacity of the cooler.
Advantageous Effects of Invention
[0042] According to the cooler of the invention, when the
semiconductor chip reaches a high temperature, the flow rate of the
refrigerant is automatically increased by the bimetal valve, and it
is thus possible to suppress a rise in the temperature of the
semiconductor chip. Also, as the cooler has a small number of parts
and a simple structure, it is easy to assemble the cooler.
BRIEF DESCRIPTION OF DRAWINGS
[0043] FIGS. 1(a)-1(c) are diagrams of a cooler of a first working
example according to the invention.
[0044] FIGS. 2(a) and 2(b) show illustrations illustrating curved
states of a bimetal valve in a first shape and a second shape.
[0045] FIGS. 3(a)-3(c) are diagrams of a semiconductor device of a
second working example according to the invention.
[0046] FIG. 4 is a main portion sectional view of a semiconductor
device of a third working example according to the invention.
[0047] FIGS. 5(a)-5(c) are diagrams wherein a heretofore known
semiconductor module is mounted on a cooler.
[0048] FIG. 6 is a diagram showing a place high in temperature in
the cooler.
DESCRIPTION OF EMBODIMENTS
[0049] A description will be given, using the drawings, of an
embodiment of the invention. The invention, not being limited to
the following working examples, can be implemented appropriately
modified without departing from the scope of the invention.
Working Example 1
[0050] FIGS. 1(a)-1(c) show one of embodiments according to a
cooler of the invention. FIG. 1(a) is a main portion plan view,
viewed through a bottom plate 21b of a jacket 21 from the rear,
FIG. 1(b) is a main portion sectional view taken along line 1 (b)-1
(b) in FIGS. 1(a), and FIG. 1(c) is a main portion sectional view
taken along the line 1(c)-1(c) in FIG. 1(a). The cooler 100b is
used to cool a semiconductor module 100a or the like. The
semiconductor module 100a is fixed to the cooler 100b via a thermal
compound 28.
[0051] The semiconductor module 100a includes circuit substrates 4
each having an insulating substrate 4a, a circuit portion 4b on the
upper surface of the insulating substrate, and a metal portion 4c
on the lower surface of the insulating substrate 4a, semiconductor
chips 8, each electrically connected to the circuit portion 4b,
which is cooled by the cooler 100b, first external terminals 9a
each being connected to the semiconductor chip 8, second external
terminals 9b each being connected to the circuit portion, and a
resin portion 10 which houses the circuit substrates 4, the
semiconductor chips 8, the first external terminals 9a, and the
second external terminals 9b, except the surfaces on the opposite
sides of the metal portions 4c from the insulating substrates 4a,
one end of each of the first external terminals 9a, and one end of
each of the second external terminals 9b. A plurality of fins 22 of
the cooler 100b is fixed to the rear surface of the top plate 20,
and is thermally connected to the semiconductor chips 8 byway of
the top plate 20, the thermal compound 28, a metal base 1, the
metal portion 4c, the insulating substrate 4a, and the circuit
portion 4b. Heat transfer pins 25 are disposed on the rear surface
of the top plate 20 which is located below the insulating
substrates 4a. Furthermore, a semiconductor device 100 of the
invention includes a plurality of intermediate assemblies 2 each
having the circuit substrate 4, the semiconductor chip 8, the first
external terminal 9a, and the second external terminal 9b, and
includes the metal base 1 disposed between a plurality of the metal
portions 4c and the top plate 20, a first connection member (not
shown) which thermally connects the plurality of metal portions 4c
and the metal base 1, and a second connection member (not shown)
which thermally connects the metal base 1 and top plate 20.
[0052] The plurality (in FIG. 1, six) of intermediate assemblies 2
is mounted on the cooler 100b via the thermal compound 28 or the
like.
[0053] The cooler 100b of the invention is a liquid cooling type
cooler which cools the semiconductor module 100a, and as a
refrigerant, without being particularly limited, a liquid, such as
water or an ethylene glycol solution, can be used. More
specifically, the cooler 100b includes the top plate 20, the jacket
21, having a side plate 21a and the bottom plate 21b, the side
plate 21a of which is firmly fixed to the top plate 20, a
refrigerant inflow port 23 through which the refrigerant flows into
a space surrounded by the top plate 20 and the jacket 21, a
refrigerant outflow port 24 through which the refrigerant flows out
from the space, the plurality of fins 22, firmly fixed to the top
plate 20 and disposed separately on each of the left and right of a
central main refrigerant path 30 in the jacket 21 which extend to
the refrigerant inflow port 23, and which are disposed to incline
toward the inflow side of the main refrigerant path 30, the heat
transfer pins 25 disposed in positions on the rear surface of the
top plate 20 on the refrigerant inflow sides of the fins 22, and a
curved plate-like bimetal valve 26, one end of which is connected
to each respective heat transfer pin 25, and the other end of which
is a free end.
[0054] As the jacket 21 is fabricated by, for example, forming a
thick flat plate into a top open casing by cutting or pressing, the
side plate 21a and the bottom plate 21b may be integrated.
[0055] The places to install the refrigerant inflow port 23 and the
refrigerant outflow port 24 are not limited to the side plate 21a.
For example, the refrigerant inflow port 23 and the refrigerant
outflow port 24 may be provided in the bottom plate 21b.
[0056] Also, the cooler 100b includes a blocking plate 34 on the
downstream side of the main refrigerant path in the center of the
jacket 21, which extends from the refrigerant inflow port 23, and
before the refrigerant outflow port 20. It is not preferable to
provide no blocking plate 34 because as the refrigerant flowing
through the main refrigerant path 30 flows directly to the
refrigerant outflow port 24, the flow rate of the refrigerant
flowing between the fins 22 is likely to decrease.
[0057] It is preferable that the installation distance between the
heat transfer pins 25 is twice or more as large as the distance
between adjacent fins 22, and in FIGS. 1(a)-1(c), the heat transfer
pins 25 and bimetal valves 26 are disposed, each skipping one fin
22. It is not effective that the bimetal valves are disposed one on
each consecutive fin because the amount of refrigerant taken in by
the downstream side bimetal valves decreases. According to this
kind of configuration, it is possible to prevent the mutual
interference between the bimetal valves.
[0058] The bimetal valves 26 can change to a first shape which is
curved in a refrigerant inflow direction, and to a second shape
which becomes closer to linear as the temperature becomes higher
than that in the first shape, and the bimetal valves 26 are formed
so that the distance between the free end of each bimetal valve 26
and the fin 22 adjacent thereto is equal to the distance between
adjacent fins 22, and are disposed so as not to make contact with
the bottom plate 21b of the jacket 21 or the top plate 20 when in
the first shape. The bimetal valves 26 curved at room temperature
behave so as to become closer to linear with a rise in temperature.
The bimetal valves 26, by becoming closer to linear, function to
block one portion of the main refrigerant path 30 and change the
stream direction so that the stream in the main refrigerant path 30
flows to the fin 22 side.
[0059] The bimetal valves 26 are formed such that a first metal
piece and a second metal piece higher in expansion coefficient than
the first metal piece are joined. As the low expansion coefficient
side first metal piece, an iron-nickel alloy plate (Invar
(trademark) or the like) is used, and as the high expansion
coefficient side second metal piece, a plate wherein one or a
plurality of metals selected from the group consisting of
manganese, chromium, and copper is added to an iron-nickel alloy
plate, is used. The bimetal valves 26 are formed by bonding the
first metal piece and the second metal piece by cold rolling. As
the thickness (the combined thickness of the first and second metal
pieces) of the bimetal valves 26, a thickness with the strength
which can withstand the stream flowing inside the cooler 100b is
selected, and it is preferred that the thickness is in a range of
0.5 mm or more and 5 mm or less. When the thickness is less than
0.5 mm, the mechanical strength is small, thus leading to the
possibility of a change in shape due to the stream. More than 5 mm
is not preferable because the heat capacity increases, and the rise
in temperature of the bimetal valves 26 is delayed, thus leading to
a decrease in temperature followability.
[0060] FIGS. 2(a) and 2(b) show illustrations illustrating curved
states of the bimetal valve 26 in the first shape and the second
shape. FIG. 2(a) is a diagram in the first shape, and FIG. 2(b) is
a diagram in the second shape.
[0061] One heat transfer pin 25 is disposed on the upstream side of
every two fins 22. By so doing, it is possible to increase the
mounting density of the bimetal valves 26, and thus possible to
reliably dispose the bimetal valves 26 below the semiconductor chip
8. Also, when the fins 22 are narrowly spaced, one heat transfer
pin 25 may be installed on every three or more fins 22. That is, it
is important that one or more bimetal valves 26 are disposed
immediately below the intermediate assembly 2 regardless of the
size of the intermediate assembly 2.
[0062] Also, an inclination angel .theta. of the fin 22 is set in a
range of 30 degrees or more and 60 degrees or less with a central
axis 30a of the main refrigerant path 30 as a reference. By so
doing, a constant amount of a refrigerant 32, which branches from a
refrigerant 31 flowing through the main refrigerant path 30 and
flows between the fins 22, flows stably and uniformly between the
fins 22, as shown in FIGS. 2(a), 2(b) to be described
hereafter.
[0063] The bimetal valve 26, one end of which is fixed to the heat
transfer pin 25, is curved concavely toward the refrigerant inflow
port 23 side when in the first shape formed at low temperature. The
concavely curved bimetal valve 26, when at high temperature,
changes in shape so as to become closer to linear and forms the
second shape, as shown in FIG. 2(b). Therefore, a leading end
portion 26a acts to block one portion of the refrigerant 31 flowing
through the main refrigerant path 30 and change the direction of
the refrigerant 31 so that the refrigerant 31 flows to the fin 22
side. Therefore, when at high temperature, the flow rate of the
refrigerant 32 flowing to the fin 22 side increases, thus
efficiently cooling the circuit substrate 4 immediately above. The
semiconductor chip 8 is cooled via the cooled circuit substrate
4.
[0064] Also, as the material of the top plate 20 and fins 22,
without being particularly limited, for example, a material with
good heat conduction, such as aluminum, is preferable. As the heat
transfer rate of the cooler when starting the semiconductor device
can be improved by reducing the thickness of the top plate, it is
possible to mount a higher power semiconductor chip. Further, it is
possible to lower the weight of the cooler, and thus possible to
reduce manufacturing cost. However, as the mechanical strength
decreases when the thickness of the top plate 20 is less than 1 mm,
it is preferable to set the thickness of the top plate 20 to 1 mm
or more.
[0065] Meanwhile, by increasing the thickness of the top plate 20,
heat generated in the semiconductor chip 8 transfers to the fins 22
in a wider range of the cooler 100b, and the area of the fins 22 in
contact with the refrigerant increases, meaning that it is possible
to enhance the cooling capacity when steadily operating the
semiconductor device. However, as the transient response
performance of the cooler 100b decreases when the thickness of the
top plate 20 is too large, there is the disadvantage that it is
difficult to mount a high power semiconductor chip. Therefore, it
is preferable that the thickness of the top plate 20 is 3 mm or
less.
[0066] In light of the heretofore described, the thickness of the
top plate 20 is preferably set to 1 mm or more and 3 mm or less,
and more preferably, to 1 mm or more and 2 mm or less.
[0067] According to the heretofore described aspect, the heat of
the semiconductor chip 8 which is being generated is transferred
via the heat transfer pins 25 to the fins 22 disposed in the cooler
100b. The heat transfers to the bimetal valve 26, the curved
bimetal valve 26 becomes closer to linear, and the free end side of
the bimetal valve 26 moves into the main refrigerant path 30. Then,
one portion of the refrigerant stream flowing through the main
refrigerant path 30 can be led between the fins 22. As a result of
this, the flow rate of the refrigerant flowing to the fin 22 side
from the main refrigerant path 30 increases, thus promoting the
cooling of the intermediate assembly 2 and cooling the
semiconductor chip 8.
[0068] As heretofore described, by installing the bimetal valves 26
on the fins 22 and adjusting the cooling capacity, it is possible
to prevent a rise in temperature of the semiconductor chip 8 and
equalize the temperature distribution of the intermediate
assemblies 2. By the portions of the intermediate assemblies 2
being uniformly cooled, it is possible to improve the output
(current capacity) of the semiconductor module 100a.
[0069] Also, as the portions of six intermediate assemblies 2
forming the semiconductor module 100a are uniform in temperature,
it is possible to reduce a change in the shape of each member due
to heat expansion, and thus possible to improve the reliability of
the semiconductor module 100a.
[0070] Herein, a more detailed description will be given of the
bimetal valve 26. When the bimetal valve 26 is in a low temperature
state (FIG. 2 (a)), it is preferable that a minimum distance P1
(the distance in a direction perpendicular to the surfaces of the
fins 22) between the free end 26a of the bimetal valve 26 and the
fin 22 adjacent to the inflow port side of the main refrigerant
path 30 is approximately once with reference to a minimum distance
T between the adjacent fins 22. Also, it is desirable that a
minimum distance Q2 (the distance in a direction perpendicular to
the central axis) between the free end 26a of the bimetal valve 26
and the central axis 30a of the main refrigerant path 30 is
substantially equal to a minimum distance Q1 (the distance in the
direction perpendicular to the central axis) between a leading end
portion 22a of the fin 22 adjacent to the refrigerant inflow port
side and the central axis 30a of the main refrigerant path 30. That
is, it is preferable that the straight line connecting the leading
end portion 22a of the fin 22 and the free end 26a of the bimetal
valve 26 is substantially parallel to the central axis 30a.
[0071] When the bimetal valve 26 is in a high temperature state
(FIG. 2(b)), the bimetal valve 26 comes closer to linear, and the
free end 26a of the bimetal valve 26 sticks out, by an amount of
sticking out .DELTA.L, into the main refrigerant path 30. Then, one
portion of the refrigerant stream in the main refrigerant path 30
is taken into the fin 22 side, and the flow rate of refrigerant on
the side of the fin 22, on the upstream side of which the bimetal
valve 26 is provided, is increased. As a result of this, the
capacity to cool the intermediate assembly 2 is improved, and the
semiconductor chip 8 is cooled.
[0072] According to Working Example 1, by providing the bimetal
valves 26 in the cooler 100b, it is possible to reduce the number
of parts compared with PTL 2 and PTL 3, thus enabling a simple
configuration.
Working Example 2
[0073] FIG. 3 is a diagram of a semiconductor device 200 of Working
Example 2 according to the invention. FIG. 3(a) is a main portion
plan view, viewed through a bottom plate 21b of a cooler 3, FIG.
3(b) is a main portion sectional side view taken along the line
3(b)-3(b) in FIG. 3(a), and FIG. 3(c) is a main portion sectional
side view taken along the line 3(c)-3(c) in FIG. 3(a).
[0074] The semiconductor device 200 having the cooler 3 includes a
plurality of intermediate assemblies 2, a cooler 3, and a resin
portion 10 sealing the intermediate assemblies 2 and the upper
surface of a top plate 20 of the cooler 3.
[0075] Each of the intermediate assemblies 2 includes an insulating
substrate 4a, a circuit portion 4b on the upper surface of the
insulating substrate, a circuit substrate 4 having a metal portion
4c on the lower surface of the insulating substrate 4a, a
semiconductor chip 8, electrically connected to the circuit portion
4b, which is cooled by the cooler 3, a first external terminal 9a
connected to the semiconductor chip 8, and a second external
terminal 9b connected to the circuit portion 4b.
[0076] The cooler 3 includes the top plate 20, a jacket 21 having a
side plate 21a and a bottom plate 21b, the side plate 21a being
firmly fixed to the top plate 20, a refrigerant inflow port 23
through which a refrigerant flows into a space surrounded by the
top plate 20 and jacket 21, a refrigerant outflow port 24 through
which the refrigerant flows out from the space, a plurality of fins
22 firmly fixed to the top plate 20 and disposed separately on each
of the left and right of a main refrigerant path in the jacket 21
to be inclined toward the inflow side of the main refrigerant path,
heat transfer pins 25 disposed in positions on the top plate 20 on
the refrigerant inflow sides of the fins, and curved plate-like
bimetal valves 26, one end of which is connected to each respective
heat transfer pin 25, and the other end of which is a free end. The
plurality of fins 22 of the cooler 3 is fixed to the rear surface
of the top plate 20, and is thermally connected to the
semiconductor chip 8 by way of the top plate 20, the metal portion
4c, the insulating substrate 4a, and the circuit portion 4b. The
heat transfer pins 25 are disposed on the rear surface of the top
plate 20 which is located below the insulating substrate 4a. The
inclination angle of the fin 22 is in a range of 30 degrees or more
and 60 degrees or less with the main refrigerant path as a
reference.
[0077] The resin portion 10 houses the circuit substrates 4a, the
semiconductor chips 8, the first external terminals 9a, and the
second external terminals 9b, except the surfaces on the opposite
side of the metal portions 4c from the insulating substrates 4a,
each one end of the first external terminals 9a, and each one end
of the second external terminals 9b.
[0078] The top plate 20 of the cooler of FIGS. 3(a)-3(c) is an
intermediate member to which the metal portions 4c on the rear
surfaces of the insulating substrates 4a are firmly fixed by a
joining material, such as a solder, and which serves as the metal
base 1. For example, the intermediate assemblies 2 each have a
configuration wherein for example, an IGBT chip and an FWD chip are
connected in inverse parallel to the circuit substrate 4, and the
first external terminal 9a and the second external terminal 9b are
disposed on the circuit substrate 4, and the intermediate
assemblies 2 are firmly fixed to the top plate 20 (the metal base
1), and subsequently, are covered with the resin portion 10, thus
completing the semiconductor module 200a. One intermediate assembly
2 can form one arm of an inverter circuit. Therefore, a three-phase
inverter circuit can be formed by using six intermediate assemblies
2.
[0079] The semiconductor device 200 is shown as a mold resin type,
but is not limited to this. There is also a case in which the
semiconductor device 200 is, for example, of a terminal case type
wherein the intermediate assemblies 2 are housed in a terminal case
in which external lead-out terminals are insert molded.
[0080] The difference between the cooler portion shown by numeral 3
shown in FIGS. 3(a)-3(c) and the cooler 100b shown in FIGS.
1(a)-1(c) is in that the metal base 1, to which the intermediate
assemblies 2 are firmly fixed, serves as the top plate 20 of the
cooler 3. As described in FIGS. 1(a)-1(c), by installing the
bimetal valves 26 on the fins 22 and adjusting the cooling
capacity, it is possible to prevent a rise in temperature of the
semiconductor chips 8 and equalize the temperature distribution of
the whole of the semiconductor device 200.
[0081] Also, at least one bimetal valve 26 is disposed in the
vicinity of the center of the insulating substrate 4a. Of course,
it is preferable to dispose a plurality of bimetal valves because
cooling efficiency is thereby further improved.
[0082] In this way, as the top plate 20 is removed by integrating
the semiconductor module 200a and cooler 3 and causing the metal
base 1 to function as the top plate 20, the heat transfer rate is
improved, and it is thus possible to improve cooling efficiency.
Therefore, it is possible to operate the semiconductor module 200
on the condition that the amount of heat generation is larger, thus
enabling high performance (for example, an increase in current
capacity).
[0083] Also, as the semiconductor device 200 has uniform
temperature, a change in shape of each member due to heat expansion
decreases, and it is thus possible to improve the reliability of
the semiconductor 200.
[0084] The explanations about the heat transfer pins 25 and bimetal
valves 26 of the cooler 100b described in FIGS. 1(a) to 2(b) also
apply to the cooler 3 of FIGS. 3(a)-3(c).
Working Example 3
[0085] FIG. 4 is a main portion sectional view of a semiconductor
device 300 of Working Example 3 according to the invention. The
difference from the semiconductor device 200 of FIGS. 3(a)-3(c) is
that the metal base 1 is removed and that the metal portion 4c on
the rear surface of an insulating substrate 4 is directly utilized
as a top plate 20 of a cooler 3a. As there is no metal base 1 or
metal portion 4c, it is possible to improve the heat transfer rate,
and thus possible to increase the cooling effect on semiconductor
chips 8. Also, it is possible to miniaturize the semiconductor
device 300. In the semiconductor device 300, the top plate 20,
which corresponds to the metal portion 4c, on the rear surface of
the insulating substrate 4 is common to intermediate assemblies
2.
[0086] According to Working Example 2 and Working Example 3, by
providing the heat transfer pins 25 and bimetal valves 26 in the
cooler 3 and integrating the cooler 3 and intermediate assemblies
2, it is possible to provide the semiconductor device 200, 300
which can be easily assembled and is improved in cooling
performance.
REFERENCE SIGNS LIST
[0087] 1, 51 metal base [0088] 2, 52 intermediate assembly [0089]
3, 3a, 100b, 500b cooler [0090] 4, 54 circuit substrate [0091] 4a,
54a insulating substrate [0092] 4b, 54b circuit portion [0093] 4c,
54c metal portion [0094] 8, 58 semiconductor chip [0095] 9a, 59a
first external terminal [0096] 9b, 59b second external terminal
[0097] 22a leading end portion [0098] 10, 60 resin portion [0099]
20, 70 top plate [0100] 21, 71 jacket [0101] 21a, 71a side plate
[0102] 21b, 71b bottom plate [0103] 22, 72 fin [0104] 23, 73
refrigerant inflow port [0105] 24, 74 refrigerant outflow port
[0106] 25 heat transfer pin [0107] 26 bimetal valve [0108] 26a free
end [0109] 28, 78 thermal compound [0110] 30 main refrigerant path
[0111] 30a central axis [0112] 34 blocking plate [0113] 80 stream
[0114] 81 place [0115] 100a, 200a, 500a semiconductor module [0116]
100, 200, 300, 500 semiconductor device [0117] P1, Q1, Q2, T
minimum distance [0118] .theta. inclination angle [0119] L length
of bimetal valve
* * * * *